Present Situation and Development of High Frequency Vibrating Screen at Home and Abroad

Vibrating screen is a high frequency, high vibration intensity as the main characteristics of the vibrating screen, mainly suitable for 0.5mm fine material wet classification and solid-liquid separation. In the coal preparation industry, because of its low investment and operating costs, most coal preparation plants have the ability to use its recovery of coal slime, so as to achieve closed-circuit washing water circulation and improve the environment of the coal preparation plant, and has obvious economic and social benefits. At present, it has been widely promoted and applied at home and abroad. 1 Research status of foreign high-frequency vibrating screen As early as the early 1950 s, foreign countries have developed high-frequency vibrating screen. In the metallurgical industry, it is used for the classification of fine iron ore in mineral processing plants; in coal processing, it is used for slime dewatering, demixing and classification. At present, foreign countries with this technology are the United States, Australia, Germany, France and Finland. Its products are also diversified, such as SLV-type high-frequency vibrating dehydration screen produced by Schenck and HF-type high-frequency vibrating screen produced by Nordberg. At present, from the literature, the vibration parameters of the high-frequency vibrating screen designed abroad are very different from each other. In combination, the vibration frequency is 24~60Hz, and the vibration intensity is 5 ~ 11gn. The high frequency vibrating screen produced abroad has the advantages of large processing capacity, high efficiency, stable performance and long service life, but the main disadvantages are high price, small processing capacity and low cost performance. At present, its maximum span is only 1.8m. Although foreign high-frequency vibrating screen models are different, but the working principle is basically similar. The following is a brief analysis of the most typical American Derek high-frequency sieve, Verco dehydrating screen and SD-type high-frequency vibrating screen. 111 Derek High Frequency Vibrating Fine Sieve Derek High Frequency Vibrating Fine Sieve was invented by Derek Company of the United States in 1951. Its structural principle is shown in Figure 1. Its structural characteristics are as follows: (1) It adopts high frequency, low amplitude (60Hz,0.8mm), positive inclination angle and large inclination angle screen surface (>30), and the screen surface has high transportation capacity. (2) The screen machine has 3 independent screen surfaces, which are fed separately. Under the condition of maintaining the same screening efficiency, compared with the single-point feeding screen, its processing capacity is 1.5 times larger. (3) The structure of the sieve chute is unique and does not hinder the sieve water from the middle and discharge end of the sieve from falling into the sieve hopper of the sieve machine. (4) The exciter is installed on the upper part of the screen box and can generate an exciting force of 60Hz. The screen surface adopts a metal wire woven sandwich screen, which has the advantage of not being easily blocked, so it is not necessary to clean it frequently. Fig. 1 structural principle of Derek high frequency vibrating screen at present, Derek high frequency vibrating screen is mainly suitable for recovering> 0.15mm fine slime from <0.5mm slime water. tests show that its suitable feed concentration is relatively low (20% ~ 40%), and the screening efficiency can even reach 88% ~ 92% without water spraying. In addition, the relevant literature shows that Derek successfully developed Urethane high-efficiency inner membrane polyester screen, Pyramid three-dimensional screen, Sandwich sandwich screen, their application, more enhanced Derek high-frequency vibrating screen processing performance of fine materials. 112 Vilco dehydrating sieve The structural principle of Vilco dehydrating sieve produced by Linnaex Company in the United States is shown in Figure 2. Its structural characteristics are as follows: (1) The slurry from the feed box is fed in an almost vertical direction. (2) The inclination angle of the sieve surface at the feeding end is> 45 °, the main sieve surface is installed at a negative inclination angle, and the whole sieve surface is in a V-shaped state. (3) The sieve surface at the feeding end and the front section of the main sieve surface adopt wedge-shaped slit sieve surface, and the discharge end adopts polyurethane sieve plate. The sieve slit gradually increases from the feeding end to the middle and then to the discharge end. (4) Two motors are installed on the bearing beam of the screen box. If the eccentric counterweight on the shaft extension at both ends of the motor is adjusted, the amplitude can be adjusted. In addition, weir plate is arranged at the discharge end to adjust the thickness of the material layer on the screen surface. Fig. 2 structural principle of virco dehydrating screen 113 SD type high frequency vibrating screen the SD type high frequency vibrating screen produced by conway company in the United States has the fastest development and the most extensive application. At present, this type of high-frequency vibrating screen has a minimum width of 0.9m and a maximum width of 1.8m. Its main features are as follows: (1) The screen surface is installed at an angle of -5, with an amplitude of 3mm and a vibration frequency of 1474r/min. Due to the climbing and walking of the material on the screen, the material on the screen has a certain thickness. Therefore, it also plays a filtering role, so that the moisture of the material is low and the particle size of the interception is smaller. (2) Adopt special G-MASTEF vibration exciter or vibration motor, and the screen surface is made of polyurethane or stainless steel seam. (3) A variety of products can be provided, the sieve body has simple structure, convenient maintenance, long service life, large processing capacity and high efficiency. 2 China's high-frequency vibrating screen research status In China, the development of high-frequency vibrating screen technology is relatively late, until the late 1970 s, only in the metallurgical system began to introduce a small amount of high-frequency vibrating screen. The development and testing of high-frequency vibrating screen in China began in the early 1980 s, and its typical research is as follows. (1): The GPS-900-3 high-frequency vibrating fine screen trial-produced by Changsha Institute of Mining and Metallurgy, Ministry of Metallurgy, in 1982 was tested in non-ferrous metal mines and achieved ideal results. Industrial tests were carried out in Miyun Iron Mine in September 1986. Compared with the original arc-shaped screen, its screening and classification efficiency was increased by more than 1 times. Later, in the early 1990 s, the GPS-1400-3-type high-frequency vibration screen was used in the Masteel Nanshan iron ore concave mountain processing plant for industrial testing, and the use of computer to establish a mathematical model between the high-frequency vibration screen process parameters, for the high-frequency vibration screen optimization control provides a basis. (2): In order to meet the needs of slime recovery and fine dewatering classification, the GPS-1025 high-frequency vibration dewatering screen designed by Tangshan Research Institute of the General Institute of Coal Science, through industrial tests in Haizhou Coal Preparation Plant in Fuxin, Liaoning Province in 1990, shows that the screen machine has reached the advanced level of similar screens in China. In 2004, QZK-1833 and QZK-2041 curved screens were successfully developed, and good technical and economic indicators were achieved on the spot. (3): In the "Seventh Five-Year Plan" science and technology project of the former Ministry of Coal, the former Pingdingshan Coal Preparation Design and Research Institute researched and designed the first GZ-631 high-frequency test screen with adjustable amplitude and frequency characteristics in March 1989. In May 1990, the test and research of vibration parameters were completed in Linxi Coal Preparation Plant, and the relationship between the vibration parameters and screening process indexes was studied. At present, high frequency vibrating screen is widely used in coal preparation industry in China. Reflected from the market, the annual demand for about 100 sets of high-frequency vibration dewatering screen, its economic and social benefits are very significant. Therefore, many large-scale vibrating screen manufacturers in China have also followed the market demand and developed many types of high-frequency vibrating dewatering screens. For example, GZ series filter layer dewatering high-frequency screen developed by Beijing Huayu Engineering Co., Ltd. (formerly Pingdingshan Coal Preparation Design Institute); QZK series curved surface screen, GPS series high-frequency screen and DZSM series electromagnetic vibration high-frequency screen developed by Tangshan Research Institute of Coal Science Research Institute; TSS series HKscreen produced by Tangshan Huili Taihang Vibration Machinery Co., Ltd.; GBHS type high frequency screen and BHS screen; shanxi Sade Screening Technology Equipment Co., Ltd. produces GPS series high-frequency vibrating dehydrating screen and GZ series high-frequency screen, etc., thus making the domestic high-frequency vibrating screen more competitive in the market. Although the models are different from each other, but the basic principle is not much different, combined, at present, China has developed the main GPS-type high-frequency linear vibrating screen, QZK series curved surface screen and DZS-type high-frequency vibrating electromagnetic fine screen. The following is a brief introduction to their respective structural characteristics. 211 GPS series high-frequency circular vibrating screen GPS series high-frequency circular vibrating screen is mainly used for the recovery of fine coal slime and works at a frequency of 50~60Hz. Its structural appearance is shown in Figure 3. Figure 3 GPS series high frequency circular vibrating screen (1) sieve machine is carried out in the thin layer and based on the precise screening of slime screening classification equipment. (2) It works according to the principle of circular vibrating screen, with a high frequency of 33.3Hz and a vibration intensity greater than 5gn. (3) The screen surface adopts the composite screen surface of the "sandwich" screen, and its opening rate can reach 36%, and the anti-blocking effect is very good. 212 GZ,GZT high-frequency linear vibrating screen The high-frequency linear vibrating screen is divided into GZ high-frequency vibrating screen and GZT low-noise high-frequency vibrating screen. The difference between the two is that the vibrator of GZ high-frequency vibrating screen is a unit combination type, while the screen frame is an integral welded structure. The vibrator of GZT low-noise high-frequency vibrating screen is a box type. In order to reduce noise, the screen frame adopts sandwich side wall and beam, the vibrator is driven by two motors respectively, and there is no forced connection between the two transmission shafts. (2) The screen surface is composed of an arc section and a negative inclination straight section. The seam of the arc section is perpendicular to the movement direction of the material, and the seam of the main screen surface is the same as the movement direction. 213 QZK series curved surface sieve QZK series curved surface sieve basic principle and GZ type similar, but the sieve surface overcomes the shortcomings of GZ type is too high, the sieve surface is generally stainless steel ladder welded sieve plate or composite sieve plate, as shown in Figure 4. Figure 4 QZK series curved screen is currently the fastest developing technology. This type of screen machine uses a working frequency of 24Hz, an amplitude of 2~2.5mm, and a vibration intensity of 5 ~ 7gn. It has the advantages of low moisture content (≤ 24%), high processing capacity and high solid recovery rate. In recent years, with the successive construction of large-scale coal preparation plants, the specifications of QZK series curved screens have been continuously innovated. At present, the QZK-2041 type is the largest model successfully applied in China, and the maximum span of this type of screen machine has reached 2.4m and the length is 4.5m, which is the largest high-frequency dewatering screen in China and the world. This kind of sieve machine adopts the structure of block eccentric vibrator and grease lubrication, and its disadvantage is that the lower limit of screening is limited, and the processing capacity per unit area is low. 214 DZS type electromagnetic vibrating fine screen electromagnetic vibrating fine screen has the advantages of light weight, low energy consumption, low classification limit, no dynamic load, mainly used for slime classification, dewatering operations, because it can recover most of the slime, in some of the slime coal quality is better, can also replace the flotation, so it has been widely used. At present, China has developed DZS type products. as shown in Figure 5. Fig. 5 DZS type electromagnetic vibrating fine screen has its main characteristics: (1)DZS type electromagnetic vibrating screen is a vibrating screen with large inclination angle and stainless steel mesh screen surface. the screen surface is directly excited by a vibration exciter while the screen box does not vibrate. due to the vibration system working in a near resonance state, the energy consumption is low. (2) The screen surface is composed of stainless steel composite screen mesh and support mesh. Each screen is arranged with several vibrators along the screen length. Each vibrator vibrates the screen surface separately. Due to the superposition of string vibration at each point, the actual amplitude of the screen surface is larger than that of the excitation point. 3 domestic and foreign high frequency vibrating screen development trend (1) to large-scale development. The large-scale of high-frequency vibrating screen refers to the large-scale motion parameters and area of the screen, mainly to solve the problem of the screening effect of materials and the processing capacity of the screen, large-scale can reduce the number and cost of screening equipment, reduce the plant area, reduce the initial infrastructure investment. (2) To reduce the quality of the development of the vibration. Through the reduction of the vibration quality, the excitation force can also be reduced, which can ensure the strength and rigidity, reduce the vibration noise, and can play a good vibration reduction effect. (3) Development towards standardization, serialization and generalization. Standardization, serialization and generalization are effective ways to facilitate design, production and cost reduction. (4) Analysis and research on the use of high frequency vibrating screen in coal preparation. At present, high-frequency vibrating screen instead of sedimentation filter centrifuge, pressure filter or diaphragm filter, flotation clean coal dewatering, instead of flotation system and recovery group slime, etc., in the practice of coal washing plant, achieved good results. In the future, its other uses in coal preparation will be analyzed and studied to improve its role in coal preparation. 4 China's high-frequency vibrating screen problems (1) the structure of the screen itself is not enough understanding. In the design process, due to the lack of understanding of the structural strength of each component, it is easy to cause stress concentration in production, resulting in side plates, support beams, sieve plates and other fracture phenomena, affecting normal production activities. (2) Slow progress in the process of large-scale design. At present, the largest model of successful application in China is QZK-2041 curved screen, and GFS-2445 curved screen is under study. However, due to insufficient understanding of the structure, it is still in a less mature stage. (3) Insufficient understanding of the relationship between the technical parameters of the high-frequency vibrating screen. Due to the lack of understanding of the relationship between the various process parameters or vibration parameters of the high-frequency vibrating screen, it is easy to make mistakes in design or selection, resulting in "running water" and "running rough" and other phenomena, thus affecting normal production. (4) The structural strength of the material cannot meet the requirements. At present, there are still many gaps between domestic and foreign research on the material, so that the life of domestic high-frequency vibrating screen is generally low, the current life is generally 3 ~ 5a, while the foreign is about 8a, resulting in increased production costs and waste of resources. Author: 11 Tangshan Research Institute of Coal Science Research Institute; 21 Anshan Sintering Plant of Angang Group Mining Company (Zhao Huanshuai 1 Wang Zhennian 2) Reference: [1] Zhao Huanshuai. Theoretical and experimental research and analysis of the main technical parameters of QZK18375 curved screen [D]. Beijing: Coal Science Research Institute, 2009. [2] Liang Jingang, Zhao Huanshuai, He Jianxin. Current situation and development trend of coal preparation technology and equipment at home and abroad [J]. Coal Preparation Technology, 2008(1):60264. [3] Wang Chengzhang. Application of High Frequency Vibrating Fine Screen in Miyun Iron Mine and Its Economic Benefit [J]. Metal Mine, 1990(2):36241. [4] Sun Yechang, Zhang Shenglong, Wang Hao, et al. Study on Mathematical Model of Under-sieve Yield of High Frequency Fine Sieve [J]. Metal Mine, 1993(3):37239.

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